WMS7140/1

Publication Release Date: April 21, 2005

- 7 -

Revision 1.1

7. FUNCTIONAL DESCRIPTION

The WMS7140/1, a nonvolatile digitally programmable potentiometers with 16 taps, with or without

output buffer, is designed to operate as both a potentiometer or a variable resistor depending upon

the output configuration selected.

The chip can store up to one 8-bit word in a nonvolatile memory (NVMEM0) in order to set the tap

register value when the device is powered up.

The WMS7140/1 is controlled by a serial Up-Down (3-wire) interface that allows setting the tap

register value as well as storing data in the nonvolatile memory.

The WMS7140/1 can operate as either a rheostat or as a potentiometer (voltage divider). When in the

potentiometer configuration there are two possible modes. One is done using WMS7140 Winpot

device without the output buffer and the other mode is done with WMS7141 WinPot device with the

output buffer.

7.1.1. Rheostat Configuration

The WMS7140/1 acts as a two terminal resistive element in the rheostat configuration where one

and the resistance can be adjusted by sending the corresponding tap register setting to the

WMS7140/1 or can also be set by loading a pre-set tap register value from nonvolatile memory

NVMEM0 upon power up.

7.1.2. Potentiometer Configuration

wiper setting. The resistance cannot be directly measured in this configuration.

The WMS7140/1 has one NVMEM position available for storing the potentiometer setting. The

NVMEM position can be directly written via the Up/Down interface. The potentiometer is loaded with

the value stored in the NVMEM0 on power up.